The present invention relates to rotary lawn mowers and blades for rotary lawn mowers and especially to a safety blade having an improved cutting action for a rotary lawn mower.
In the past, a variety of rotary lawn mowers have been provided with various types of cutting blades. Typically, a rotary lawn mower has a single, elongated cutting blade attached to a rotary shaft and protected by a covering or housing with only the end portions having a sharpened edge, so that the fast rotation of the blade will cut the grass as the mower rolls over the grass. In addition, the blade will direct grass out a side opening in the lawn mower to a grass catcher. These types of blades have been satisfactory in that they have been inexpensive to manufacture, and easy to sharpen. However, they tend to become dull rapidly from the cutting of grass and from other collisions with sticks, rocks, and the like. The fast moving blade can drive a rock, or other solid objects, at a high velocity causing great damage to persons or property if not captured by the mower housing. Finally, a person's hand or foot getting under the housing or into the housing from the grass outlet can be severely injured if it comes in the path of the blade. These problems have resulted in great concern by manufacturers and safety groups because of the large number of injuries every year resulting from rotary mowers. In contrast to these prior art mowers, the present invention, advantageously, reduces the power required to operate a rotary blade lawn mower, while preventing the easy entry of a person's hand or foot, and at the same time, tends to spin objects, such as rocks, in place when hit by the rotary blade.
Typical prior art lawn mowers which provide improvements over the standard rotary lawn mower may be seen in U.S. Pat. No. 3,096,608, to Williamson, for a Safety Blade Assembly for Rotary Mowers, in which a standard, elongated cutting blade has a circular band attached to the end thereof to prevent the throwing of rocks from the rotary blade and to prevent the insertion of a hand or a foot into the rotating blade. U.S. Pat. No. 3,176,455, to Buchanan, for a Rotary Mower Blade and U.S. Pat. No. 2,898,725, to Roesel, for a Rotary Mower Cutting Blade Structure, and U.S. Pat. No. 3,621,642, to Leake, for a Rotary Head Cutter Assembly for Lawn Mowers, illustrate various types of lawn mowers and cutting blades, each having circular components, but with the blade portions extending horizontally from the blade supports. The Buchanan patent has an arbor saw-type blade, while the Leake patent has removable cutting elements and the Roesel patent has blades with a plurality of cutting edges which can be shifted between cutting positions. The U.S. Patent to Berry, U.S. Pat. No. 2,936,564, teaches a blade unit for rotary brush cutters in which a conventional, elongated blade has a pair of vertically extending blades with upper and lower cutting edges attached thereto in an arcuate pattern facing the direction of the rotation of the blade; and the Cummings U.S. Pat. No. 3,849,975, illustrates a cutting means employing an eccentric rotational cutting action having a pair of cutting edges acting on an eccentric pattern to provide a continuous cutting in the rotation of the blades.